The objective of this study is to develop an in vitro culture system to support normal development of early stage embryos to blastocyst stages. A series of four experiments are proposed in which four treatments; 1) bovine trophoblastic vesicles, 2) fetal bovine uterine cells, 3) oviductal epithelial cells and 4) shell-free chick embryos are used as feeder cells to co-culture with either mouse or goat embryos. In Experiment I, 1- and 2-cell mouse embryos will be used to compare the co-culture systems using Whitten's medium as the culture medium. Experiment II will be similar in design except that half of the embryos within each of the treatments will be cultured in Ham's F-10 medium while the remaining embryos within each treatment will be grown in CMRL- 1066 medium. In Experiment III goat embryos will be used to test the quality of the culture systems. The fourth experiment will be based on the results of the first three and perform a final evaluation of the co-culture systems, again using the goat as a model system. The long term goal of this research is to apply these results to the culture of early bovine embryos. The Phase II research will attempt to optimize the culture conditions and identify growth factors important to embryo development.